The present invention relates generally to the field of merged read/write magnetic heads. In particular, the present invention relates to a magnetic head for perpendicular recording having a writer portion with suppressed side writing and erasing.
In an electronic data storage and retrieval system, a transducing head typically includes a writer for storing magnetically-encoded information on a magnetic disc and a reader for retrieving that magnetically-encoded information from the magnetic disc. The reader typically consists of two shields and a magnetoresistive (MR) sensor positioned between the shields. Magnetic flux from the surface of the disc causes oscillation of the magnetization vector of a sensing layer of the MR sensor, which in turn causes a change in electrical resistivity of the MR sensor. This change in resistivity of the MR sensor can be detected by passing a current through the MR sensor and measuring a voltage across the MR sensor. External circuitry then converts the voltage information into an appropriate format and manipulates that information as necessary.
For a perpendicular recording head, the writer portion typically consists of a main pole and a return pole, which are separated from each other at an air bearing surface of the writer by a gap layer, and which are connected to each other at a region distal from the air bearing surface by a back gap closer or back via. One or more layers of conductive coils are positioned between the main and return poles, and are encapsulated by insulating layers. The writer portion and the reader portion may be arranged in a merged configuration in which a shared pole serves as both the top shield in the reader portion and the return pole in the writer portion.
To write data to the magnetic media, an electric current is caused to flow through the conductive coils to induce a magnetic field across the write gap between the main and return poles. By reversing the direction of the current through the coils, the polarity of the data written to the magnetic media is reversed. Because the main pole is generally the trailing pole of the main and return poles, the main pole is used to physically write the data to the magnetic media. Accordingly, it is the main pole that defines the track width of the written data. More specifically, the track width is defined by the width of the main pole at the air bearing surface.
In conventional perpendicular recording heads, the main pole and the return pole are fabricated such that their magnetizations point in the same direction parallel to the ABS. Due to the magnetization directions of return pole and main pole, magnetic flux emanates from the side edges of main pole and tends to close through an upper portion of the return pole. As magnetic flux closes from the main pole through the return pole, the magnetization in an upper portion of the return pole reverses direction to align with magnetic flux direction. This results in the formation of domain wall in the upper portion of the return pole under the main pole. Fringing fields emanate from the domain wall that forms in the return pole. The soft magnetic underlayer of double-layer perpendicular recording media magnifies these fringing fields. The fringing fields can be strong enough to partially or completely erase information recorded on adjacent tracks of the recording medium. Thus, there is a need in the art for a merged read/write head for perpendicular recording with suppressed side writing and erasing caused by domain walls in the return pole.